I sure do agree that it can be a place to start for many shooters. I often have done just so, then a while back (after some years of experience and match shooting) decided that I did know a little something about this game, so my 'initial' trial, especially with heavy kickers, is offhand. With .727 Ol' Ugly Overkill (OK, a smooth 12ga. sluggun)it hits pretty much where Im looking offhand (and with a recoil similar to a light .375H&H, I will not bench it, I dont need the abuse). I KNOW that off the bench it will 'pull' to the side; and that it is me in recoil, not the gun. Other than patterning a shotgun, I dont believe any shotgun shooters test their guns off a bench to know how to 'hold' to hit birds.
A bench certainly has its place, but I think the OP will have better luck seeing what the gun/load does by shooting offhand (and it will hurt less!).